Optimizing the properties of electromagnetic energy in a medium using stochastic parallel perturbation gradient descent optimization adaptive optics

ABSTRACT

A method optimizes electromagnetic energy in a system for processing an image of an object in order to perform a procedure on an object. A plurality of light beams formed of incoherent light is applied to an object at a plurality of differing frequencies and reflected from the object to provide a plurality of reflected light beams. A corresponding plurality of electrical signals is provided accordingly and a corresponding plurality of image quality metrics is determined. A corresponding plurality of images is determined in accordance with the plurality of image quality metrics and an image is selected according to a predetermined image criterion to provide a selected image. A frequency is determined according to the selected image and the procedure is performed on an object according to the determined frequency.

RELATED APPLICATION

[0001] This application is a Continuation-In-Part of U.S. patentapplication Ser. No. 10/011,187, filed on Nov. 13, 2001 entitledHIGH-RESOLUTION RETINA IMAGING AND EYE ABERRATION DIAGNOSTICS USINGSTOCHASTIC PARALLEL PERTURBATION GRADIENT DESCENT OPTIMIZATION ADAPTIVEOPTICS, whose disclosure is incorporated by reference herein.

BACKGROUND OF THE INVENTION

[0002] 1. Field of Invention

[0003] This invention relates to a method and a system forhigh-resolution retinal imaging, eye aberration compensation, anddiagnostics based on adaptive optics with direct optimization of animage quality metric using a stochastic parallel perturbative gradientdescent technique.

[0004] Adaptive optics is a promising technique for both diagnostics ofoptical aberrations of the eye and substantially aberration-freehigh-resolution imaging of the retina. In existing adaptive opticstechniques adaptive correction is based on illumination of the retina bya collimated laser beam to create a small size laser location on theretina surface with consequent measurement of phase aberrations of thewave scattered by the retina tissue. Correction of eye opticalaberrations is then performed using the conventional phase conjugationtechnique.

[0005] This traditional approach has several important drawbacks. Oneimportant drawback is the danger due to an invasive use of the laserbeam focused onto the retina. Other drawbacks include overall systemcomplexity and the high cost of the necessary adaptive optics elementssuch as a wavefront sensor and wavefront reconstruction hardware. Moreimportantly, due to aberrations the laser beam location size on theretina is not small enough to use it as a reference point-type lightsource and hence conjugation of the measured wavefront does not resultin optimal optical aberration correction. Additionally, the traditionalapproach can produce a turbid image that can make performing anoperation with a microscope difficult.

[0006] One prior art method using a laser is taught in U.S. Pat. No.6,095,651 entitled “Method and Apparatus for Improving Vision and theResolution of Retinal Images”, issued to Williams, et al. on Aug. 1,2000. In Williams, et al. teaches a method and apparatus for improvingresolution of retinal images. In this method, a point source of light isproduced on the retina by a laser beam. The source is reflected from theretina and received at a lenslet array of a Hartman-Shack wavefrontsensor. Thus, higher order aberrations of the eye can be measured anddata can be obtained for compensating the aberrations using a systemincluding a laser. U.S. Pat. Nos. 5,777,719 and 5,949,521 provideessentially the same teachings. While these references teachsatisfactory methods for compensating aberrations, there is some smallrisk of damaging the retina since these methods require applying laserbeams to the retina.

[0007] U.S. Pat. No. 5,912,731, entitled “Hartmann-type OpticalWavefront Sensor” issued to DeLong, et al. on Jun. 5, 1999 teaches anadaptive optics system using adjustable optical elements to compensatefor aberrations in an optical beam. The aberrations may be caused, forexample, by propagation of the beam through the atmosphere. Theaberrated beam can be reflected from a deformable mirror having manysmall elements, each having an associated separate actuator.

[0008] Part of the reflected beam taught by DeLong can be split off anddirected to impinge on a sensor array which provides measurementsindicative of the wavefront distortion in the reflected beam. Thewavefront distortion measurements can then be fed back to the deformablemirror to provide continuous corrections by appropriately moving themirror elements. Configurations such as this, wherein the array of smalllenses as referred to as a lenslet array, can be referred to asShack-Hartmann wavefront sensors.

[0009] Additionally, DeLong teaches a wavefront sensor for use inmeasuring local phase tilt in two dimensions over an optical beam crosssection, using only one lenslet arrangement and one camera sensor array.The measurements of DeLong are made with respect to first and secondorthogonal sets of grid lines intersecting at points of interestcorresponding to positions of optical device actuators. While thismethod does teach the way to correct aberrations in a non-laser lightsystem, it cannot be used in cases where lasers are required.

[0010] U.S. Pat. No. 6,007,204 issued to Fahrenkrug, et al. entitled“Compact Ocular Measuring System”, issued on Dec. 28, 1999, teaches amethod for determining refractive aberrations of the eye. In the systemtaught by Fahrenkrug, et al. a beam of light is focused at the back ofthe eye of the patient so that a return light path from the eye impingesupon a sensor having a light detecting surface. A micro optics array isdisposed between the sensor and the eye along the light path. Thelenslets of the micro optics array focus incremental portions of theoutgoing wavefront onto the light detecting surface so that thedeviations and the positions of the focused portions can be measured. Apair of conjugate lenses having differing focal lengths is also disposedalong the light path between the eye and the micro optics array.

[0011] U.S. Pat. No. 6,019,472, issued to Koester, et al. entitled“Contact Lens Element For Examination or Treatment of Ocular Tissues”issued on Feb. 1, 2000 teaches a multi-layered contact lens elementincluding a plurality of lens elements wherein a first lens element hasa recess capable of holding a volume of liquid against a cornea of theeye. A microscope is connected to the contact lens element to assist inthe examination or treatment of ocular tissues.

[0012] U.S. Pat. No. 6,086,204, issued to Magnante entitled “Methods andDevices To Design and Fabricate Surfaces on Contact Lenses and OnCorneal Tissue That Correct the Eyes Optical Aberrations” on Jul. 11,2000. Magnante teaches a method for measuring the optical aberrations ofan eye either with or without a contact lens in place on the cornea. Amathematical analysis is performed on the optical aberrations of the eyeto design a modified shape for the original contact lens or cornea thatwill correct the optical aberrations. An aberration correcting surfaceis fabricated on the contact lense by a process that includes laserablation and thermal molding. The source of light can be coherent orincoherent.

[0013] U.S. Pat. No. 6,143,011, issued to Hood, et al. entitled“Hydrokeratome For Refractive Surgery” issued on Nov. 7, 2000 teaches ahigh speed liquid jet for forming an ophthalmic incisions. The Hood, etal. system is adapted for high precision positioning of the jet carrier.An airway beam may be provided by a collimated LED or laser diode. Thelaser beam can be used to align the system.

[0014] U.S. Pat. No. 6,155,684, issued to Billie, et al. entitled“Method and Apparatus for Precompensating The Refractive Properties ofthe Human Eye With Adaptive Optical Feedback Control” issued on Dec. 5,2000. Billie, et al. teaches a system for directing a beam of lightthrough the eye and reflecting the light from the retina. A lensletarray is used to obtain a digitized acuity map from the reflected lightfor generating a signal that programs an active mirror. In accordancewith the signal the optical paths of individuals beams in and the beamof light are made to appear to be substantially equal to each other.Thus, the incoming beam can be precompensated to allow for therefractive aberrations of the eyes that are evidenced by the acuity map.

[0015] Additional methods for using adaptive optics to compensate foraberrations of the human eye are taught in J. Liang, D. Williams and D.Miller, “Supernormal Vision and High-Resolution Retinal Imaging ThroughAdaptive Optics,” J. Opt. Soc. Am. A, Vol. 14, No. 11, pp. 2884-2891,1997 and F. Vargas-Martin, P. Prieto, and P. Artal, “Correction of theAberrations in the Human Eye with a Liquid-Crystal Spatial LightModulator: Limits to Performance,” J. Opt. Soc. Am. A, Vol. 15, No. 9,pp.2552-2561,1998. Additionally, J. Liang, B. Grimm, S. Goelz, and J.Bille, “Objective Measurement of Wave Aberrations of the Human Eye withthe Use of a Hartmann-Shack Wave-Front Sensor,” J. Opt. Soc. Am. A, Vol.11, No. 7, pp. 1949-1957, 1994 teaches such a use of adaptive optics.

[0016] Furthermore, it is known in the art to use a PSPGD optimizationalgorithm in different applications. For example, see M. Vorontsov, andV. Sivokon, “Stochastic Parallel-Gradient-Descent Technique forHigh-Resolution Wave-Front Phase-Distortion Correction,” J. Opt. Soc.Am. A, Vol. 15, No. 10, pp. 2745-2758, 1998. Also see M. Vorontsov, G.Carhart, and J. Ricklin, “Adaptive Phase-Distortion Correction Based onParallel Gradient-Descent Optimization,” Optics Letters, Vol. 22, No.12, pp. 907-909, 1997.

[0017] It is well known in the art to scan an iris and obtain an irisbiometric image. See, for example, U.S. Pat. Nos. 4,641,349,5,291,560,5,359,669, 5,719,950, 6,289,113,6,377,699, 6,526,160, 6,532,298,6,539,100, 6,542,624, 6,546,121, 6,549,118, 6,556,699, 6,594,377,6,614,919, and U.S. Patent Application Nos. 20010026632A1,20020080256A1, 20030095689A1, 20030120934A1, 20020057438A1,20020132663A1, 20030018522A1, 20020158750A1. However, such images wereoften not optimal and their applicability was somewhat limited.

[0018] 2. Description of Related Art

[0019] All references cited herein are incorporated herein by referencein their entireties.

BRIEF SUMMARY OF THE INVENTION

[0020] The invention includes a method for clarifying an optical/digitalimage of an object to perform a procedure on an object having the stepsof applying to the object a light beam formed of incoherent light andreflecting the applied incoherent light beam from the object to providea reflected light beam and providing electrical signals representativeof the reflected light beam. An image quality metric is determined inaccordance with the electrical signals and an image is determined inaccordance with the image quality metric. The procedure is performed inaccordance with the image quality metric.

[0021] In a further method of the invention a procedure is performed onan eye having an iris. An iris biometric image representative of theiris is obtained and the procedure is performed on an eye in accordancewith the iris biometric image.

[0022] Additionally a method for optimizing electromagnetic energy in asystem for processing an image of an object in order to perform aprocedure on an object is provided. The method includes applying to theobject a plurality of light beams formed of incoherent light at aplurality of differing frequencies and reflecting the plurality ofapplied incoherent light beams from the object to provide a plurality ofreflected light beams. The method also includes providing acorresponding plurality of electrical signals representative of thereflected light beams of the plurality of reflected light beams anddetermining a corresponding plurality of image quality metrics inaccordance with the plurality of electrical signals. A correspondingplurality of images is determined in accordance with the plurality ofimage quality metrics and an image of the plurality of images isselected in accordance with a predetermined image criterion to provide aselected image. The method also includes determining a frequency of theplurality of differing frequencies in accordance with the selected imageto provide a determined frequency and performing the procedure on anobject in accordance with the determined frequency.

[0023] The inventions also deals with new methods of high-resolutionimaging and construction of images of the retina, and adaptivecorrection and diagnostics of eye optical aberrations, as well as suchimaging of articles of manufacture, identifying articles and controllinga manufacturing process. Additionally, the method is applicable toidentifying individuals in accordance with such images for medicalpurposes and for security purposes, such as a verification of anidentity of an individual. These applications can be performed usingadaptive optics techniques based on parallel stochastic perturbativegradient descent (PSPGD) optimization. This method of optimization isalso known as simultaneous perturbation stochastic approximation (SPSA)optimization. Compensation of optical aberrations of the eye andimprovement of retina image resolution can be accomplished using anelectronically controlled phase spatial light modulator (SLM) as awavefront aberration correction interfaced with an imaging sensor and afeedback controller that implements the PSPGD control algorithm.Examples of the electronically-controlled phase SLMs include a pixelizedliquid-crystal device, micro mechanical mirror array, and deformable,piston or tip-tilt mirrors. Wavefront sensing can be performed at theSLM and the wavefront aberration compensation is performed using retinaimage data obtained with an imaging camera (CCD, CMOS etc.) or with aspecially designed very large scale integration imaging chip (VLSIimager). The retina imaging data are processed to obtain a signalcharacterizing the quality of the retinal image (image quality metric)used to control the wavefront correction and compensate the eyeaberrations.

[0024] The image quality computation can be performed externally usingan imaging sensor connected with a computer or internally directly on animaging chip. The image quality metric signal is used as an input signalfor the feedback controller. The controller computes control voltagesapplied to the wavefront aberration correction. The controller can beimplemented as a computer module, a field programmable gate array (FPGA)or a VLSI micro-electronic system performing computations required foroptimization of image quality metrics based on the PSPGD algorithm.

[0025] The use of the PSPGD optimization technique for adaptivecompensation of eye aberration provides considerable performanceimprovement if compared with the existing techniques for retina imagingand eye aberration compensation and diagnostics, and therapeuticapplications. The first advantage is that the PSPGD algorithm does notrequire the use of laser illumination of the retina and consequentlysignificantly reduces the risk of retina damage caused by a focusedcoherent laser beam. A further advantage is that the PSPGD algorithmdoes not require the use of a wavefront sensor or wavefront aberrationreconstruction computation. This makes the entire system low-cost andcompact if compared with the existing adaptive optics systems for retinaimaging. Additionally, the PSPGD algorithm can be implemented using aparallel analog, mix-mode analog-digital or parallel digital controllerbecause of its parallel nature. This significantly speeds up theoperations of the PSPGD algorithm, providing continuous retina imageimprovement, eye aberration compensation and diagnostics.

[0026] Thus, in the adaptive correction technique of the presentinvention neither laser illumination nor wavefront sensing are required.Optical aberration correction is based on direct optimization of thequality of an retina image obtained using a white light, incoherent,partially coherent imaging system. The novel imaging system includes amulti-electrode phase spatial light modulator, or an adaptive mirrorcontrolled with a computer or with a specially designed FPGA or VLSIsystem. The calculated image quality metric is optimized using aparallel stochastic gradient descent algorithm. The adaptive opticalsystem is used in order to compensate severe optical aberrations of theeye and thus provide a high-resolution image and/or of the retina tissueand the eye aberration diagnostic.

BRIEF DESCRIPTION OF SEVERAL VIEWS OF THE DRAWINGS

[0027] The invention will be described in conjunction with the followingdrawings in which like reference numerals designate like elements andwherein:

[0028]FIGS. 1A,B show a schematic representation of system suitable forpracticing the eye aberration correcting method of the presentinvention.

[0029]FIG. 2 shows a flow chart representation of control algorithmsuitable for use in the system of FIG. 1 when practicing the method ofthe present invention.

[0030]FIGS. 3A,B show images of an artificial retina before and aftercorrection of an aberration

[0031]FIGS. 4A,B show an eye and a biometric image of the iris of theeye.

[0032]FIG. 5 shows a block diagram representation of an iris biometricimage comparison system which can be used with the aberration correctingsystem of FIG. 1.

[0033]FIG. 6 shows a block diagram representation of an iris positioningsystem which can be used in cooperation with the aberration correctingsystem of FIG. 1.

[0034]FIG. 7 shows an illumination frequency optimization system whichcan be used in cooperation with the aberration correcting system of FIG.1.

[0035]FIG. 8 shows an image superpositioning system which can be usedwith the aberration correcting system of FIG. 1.

DETAILED DESCRIPTION OF THE INVENTION

[0036] Referring now to FIGS. 1A,B there are shown schematicrepresentations of the aberration correcting system 10 of the presentinvention. In the aberration correcting system 10 a light beam from awhite light source 1 is redirected by a mirror 2 in order to cause it toenter an eye. In accordance with the present invention the white lightbeam from the light source 1 can be any kind of incoherent light.

[0037] The light from the mirror 2 reaches the retina 4 of the eye andreflected light exits the eye to provide two light beams, one passing ineach direction, as indicated by arrow 3. The exiting light beam thenpasses through an SLM 5. The light beam from the SLM 5 enters an imagesensor 6. The image sensor 6 can be a charge coupled capacitor device orany other device capable of sensing and digitizing the light beam fromthe SLM 5.

[0038] The imaging sensor 6 can include an imaging chip for performingthe calculations required to determine an image quality metric. Theimage quality metric can thus be computed on the imaging chip directlyor it can be calculated using a separate computational device/computer 7that calculates the image quality metric of the retina image. It is theuse of a digitized image in this manner that permits the use of anincoherent light rather than a coherent light for performing theoperations of the aberration correction correcting system 10.

[0039] The computational device 7 sends a measurement signalrepresentative of the image quality metric to a controller 8. Thecontroller 8 implements a PSPGD algorithm by computing control voltagesand applying the computed control voltages to the SLM 5. The PSPGDalgorithm used by the controller 8 can be any conventional PSPGDalgorithm known to those of ordinary skill in the art. In the preferredembodiment of the invention, the controller 8 continuously receivesdigital information about the quality of the image and continuouslyupdates the control voltages applied to the SLM 5 until the quality ofthe retina image is optimized according to predetermined image qualityoptimization criteria.

[0040] Referring now to FIGS. 2 and 3A,B there are shown a flow chartrepresentation of a portion of a PSPGD control algorithm 20 for use incooperation with the aberration correcting system 10 in order topractice the present invention as well as representations of thecorrected image, both before correction (3A) and after correction (3B).In order to simplify the drawing a single iterative step of the PSPGDcontrol algorithm 20 is shown with a loop for repeating the singleiterative step until the quality of the compensation is acceptable.

[0041] In step 25 of the PSPGD control algorithm 20 a measurement andcalculation of the image quality metric is performed. This step includesthe retinal image capture performed by the sensor 5 and the calculationof the image quality metric performed by the computational device 7within the aberration correcting system 10. The image captured by thesensor 5 at the beginning of the operation of the PSPGD controlalgorithm 20 can be substantially as shown in FIG. 3A, as previouslydescribed. One can use any relevant metric entity as an image qualitymetric. For example, in one embodiment of the PSPGD control algorithm 20the image quality metric can be a sharpness function. A sharpnessfunction suitable for use in the present invention can be defined as

J=∫|∇ ² I(x,y)|dxdy

[0042] where I(x,y) is the intensity distribution in the image, and ∇²is the Laplacian operator over the image. The Laplacian can becalculated by convolving the image with a Laplacian kernel. Theconvolving of the image can be performed by a special purpose VLSImicrochip. Alternately, the convolving of the image can be performedusing a computer that receives an image from a digital camera asdescribed in more detail below. In another embodiment different digitalhigh-pass filters can be used rather than the Laplacian operator.

[0043] Additionally, a frequency distribution function can be usedrather than a sharpness function when determining the image qualitymetric. The use of a frequency distribution function allows the systemto distinguish tissues of different colors. This is useful wheredifferent kinds of tissue, for example, different tumors, have differentcolors. Locating tumors in this manner also permits the invention toprovide tumor location information, such as a grid location on a gridhaving a pre-determined reference in order to assist in diagnosis andsurgery. It also permits the invention to provide tumor size and typeinformation. Additionally, the use of a frequency distribution functionpermits a surgeon to determine which light frequencies are best forperforming diagnosis and surgery.

[0044] The image quality metric J can also be calculated eitheroptically or digitally using the expression introduced in:

J=∫|F{exp[iγI(x,y)]}|⁴ dxdy

[0045] where F is the Fourier transform operator and ã is a parameterthat is dependent upon the dynamic range of the used image.

[0046] In step 30 of the PSPGD control algorithm 20 random perturbationsin the voltages applied to the SLM 5 electrodes are generated. The SLM 5can be a liquid crystal membrane for modifying the light beam accordingto the electrical signals from controller 8 in a manner well understoodby those skilled in the art.

[0047] In order to generate the perturbations for application to theelectrodes for the SLM 5 random numbers with any statistical propertiescan be used as perturbations. For example, uncorrelated random coin flipperturbations having identical amplitudes |u_(j) and the Bernoulliprobability distribution:

du _(j) =±p, Pr(du _(j) =+p)=0.5

[0048] for all j=1, . . . , N (N=the number of control channels) anditeration numbers can be used. Note that Non-Bernoulli perturbations arealso allowed in the PSPGD control algorithm 20.

[0049] In step 35 of the PSPGD control algorithm 20 a measurement of theperturbed image quality metric and a computation of the image qualityperturbation δJ^((m)) are performed. Following the determination of theperturbed image quality metric, the gradient estimations

{tilde over (J)} _(j)′^((m)=δ) J ^((m))π_(j) ^((m))

[0050] are computed as shown in step 40.

[0051] The updated control voltages are then determined as shown in step45. Therefore, a calculation of:

u _(j) ^((m+1)) =u _(j) ^((m)) −γδJ ^((m))π_(j) ^((m))

[0052] is performed.

[0053] To further improve the accuracy of gradient estimation in thePSPGD control algorithm 20 a two-sided perturbation can be used. In atwo-sided perturbation two measurements of the cost functionperturbations J⁺ and J⁻ are taken. The two measurements correspond tosequentially applied differential perturbations +u_(j)/2 and −u_(j)/2.It follows that:

dJ=dJ ⁺ −dJ ⁻

and

{tilde over (J)} _(j) ′=δJδu _(j)

[0054] which can produce a more accurate gradient estimate.

[0055] The process steps 25-45 of the PSPGD control algorithm 20 arerepeated interactively until the image quality metric has reached anacceptable level as determined in step 50. The choice of an acceptablelevel of the image quality metric is a conventional one well known tothose skilled in the art. As shown in step 55 the aberration is thencorrected and an image of the retina can be taken. The image resultingfrom the operation of the PSPGD algorithm 20 can be as shown in FIG. 3B.

[0056] The eye aberration function (x,y) can be calculated from knownvoltages applied to wavefront correction {u_(j)} at the end of theiterative optimization process and known response functions of{S_(j)(x,y)} wavefront correction.${j\left( {x,y} \right)} = {\sum\limits_{j = 1}^{N}\quad {u_{j}{{S_{j}\left( {x,y} \right)}.}}}$

[0057] Referring now to FIGS. 4A,B, there is shown an eye 80 having aniris 84 with a pupil 88 therein and an iris biometric image 90. The irisbiometric image 90 is a biometric image of the iris 84, which can beobtained using an iris scanning system, such as the aberrationcorrecting system 10. In an alternate embodiment of the invention, theiris biometric image 90 can be obtained by any other system (not shown)capable of scanning and digitizing an iris and providing an image thatis characteristic of the iris, such as a bar code type output as shownin FIG. 4B. Furthermore, it will be understood that every human eye hasan unique iris biometric image when it is scanned and digitized in thismanner. Thus, an iris biometric image can be used as a unique identifierof an individual in the manner that fingerprints are used or even todistinguish between the left and right eyes of an individual.

[0058] When the predetermined image quality is obtained, a plurality oflocations 92 within the iris 84 can be defined. In one preferredembodiment of the invention, four locations 92 can be selected. The fourlocations 92 can be disposed on the corners of a rectangle which isconcentric with the iris 84. The locations 92 can thus be easily used tofind the center of the iris 84. The four locations 92 are represented onthe iris biometric image 90 in accordance with the mathematicalrelationships previously described. Thus, the xy coordinates of thelocations 92 maybe mapped into corresponding xy coordinates within theiris biometric image 90 if a spatial transform such as the sharpnessfunction is used, while they may be convolved over areas of the irisbiometric image 90 if a frequency or other transform is used.

[0059] Various features already occurring in the eye 80 also havecorresponding representations within the iris biometric image 90. Thelocation and study of such features can be used to diagnose pathologies,for example, to diagnose tumors and to determine the position of the eyeiris 84. As a further example, a feature can be studied several timesover a period of time to determine how its parameters are is changing.

[0060] Referring now to FIG. 5, there is shown the iris biometric imagecomparison system 100. The iris biometric image comparison system 100receives the previously determined iris biometric image 90 as one of itsinputs. Additionally, a new iris biometric image 95 is produced, forexample, before or during the performance of a procedure on the eye 80.The new iris biometric image 95 is received by the image comparisonsystem 100 as a second input. The new iris biometric image 95 can beprovided by the aberration correction system 10. The light beam used toobtain the iris biometric image 95 can be the same light beam being usedfor other purposes during the procedure.

[0061] When using the aberration correcting system 10, the image can beoptimized by executing additional iterations of the PSPGD controlalgorithm 20. The algorithm can be iterated until a predetermined imagequality is obtained and computing the image quality metric within thecomputer 7 as previously described. In addition to performing moreiterations of the PSPGD control algorithm 20, increased imagesensitivity quality can be obtained by increasing the number of pixelsin the digitized image or increase image sensitivity can be obtained byincreasing the number of measuring points in the iris 84.

[0062] When performing the method of the image comparison system 100 theiris biometric image 90 can be assumed by the image comparison system100 to be the correct iris biometric image of the iris 84 upon which theprocedure is to be performed. Furthermore, it can be assumed that theiris biometric image 90 applied to the image comparison system 100 wasobtained when the position and orientation of the eye 80 were correct.

[0063] The iris biometric images 90, 95 are compared by the imagecomparison system 100 at decision 104. A determination is made as towhether the iris biometric image 95 is an image of the same iris 84 thatwas imaged to produce the enrolled iris biometric image 90. Any of thewell known correlation techniques can be used for the comparison.Substantially similar correlation techniques can be used for thecomparison if the locations 92 are used or if other markings within theiris 84 are used. The sensitivity of the comparison can be adjusted bythose skilled in the art.

[0064] If the determination of decision 104 is negative, then theprocedure being performed on the eye 80 is not continued as shown inblock 102. If the determination of decision 104 is positive, then adetermination can be made in decision 106 whether the iris 84 ispositioned in the xy directions correctly and oriented or rotatedcorrectly at the time that the iris biometric image 95 was produced. Thedetermination of decision 106 can be used for a number of purposed. Forexample, it could be used to direct a beam of light to a predeterminedlocation within the eye 80. Thus, if the determination of decision 106is negative, the beam can be redirected as shown in block 110. Theposition of the iris 84 can be checked again in decision 106. When theposition of the iris 84 is correct, the procedure can begin, as shown inblock 112.

[0065] The determination of decision 106 can be made in accordance withthe representations of locations 92 within the iris 84 selected wheniris biometric image 90 was obtained. If corresponding locations arefound in the iris biometric image 95 in the same positions, thedetermination of decision 106 is positive. Alternately, thedetermination of decision 106 can be made in accordance withpredetermined features or markings within the iris 84 other than thelocations 92. The method of the image comparison system 100 can be usedto determine whether the iris 84 is rotated or translated in thedirection of either of the axes orthogonal to the arrow 3 shown in FIGS.1A,B.

[0066] Referring now to FIG. 6, there is shown the iris positioningsystem 120. The iris positioning system 120 is adapted to preciselyposition the iris 84 while performing a procedure on the eye 80. Theiris positioning system 120 differs from the iris biometric imagecomparison system 100 primarily in the fact that the iris positioningsystem 120 is provided with a servo 124. The servo 124 is effective inmodifying the relative positions of the iris 84 and the camera 6 of theaberration correcting system 10 which can be coupled to equipment (notshown) used to perform the procedure in the eye.

[0067] In the iris positioning system 120 a determination is made indecision 104 whether the iris biometric images 90, 95 were made on thesame eye as previously described with respect to image comparison system100. The procedure is continued only if a positive determination ismade. A determination is then made in decision 106 whether the iris 84is in the correct position. The determination of decision 106 can bemade by comparing the iris biometric images 90, 95 in accordance withthe locations 92 or any other markings within the iris 84 as previouslydescribed. The determination made can be, for example, whether the iris84 is rotated or translated in the x or y direction at the time that theiris biometric image 95 is obtained.

[0068] When a determination is made that the iris 84 is in an incorrectposition, a correction signal representative of the error is calculated.The error correction signal is applied to the servo 124. The servo 124is adapted to receive the error correction signal resulting from thedeterminations of decision 106 and to adjust the relative positions ofthe iris 84 and the equipment performing the procedure in accordancewith the signal in a manner well understood by those skilled in the art.Servos 124 capable of applying both rotational and multi-axistranslational corrections are both provided in the preferred embodimentof the invention. Either the object such as the iris 84 or the equipmentcan be moved in response to the determination of decision 106.

[0069] The method of the iris positioning system 120 can be repeatedlyperformed, or constantly performed, during the performance of aprocedure on the eye 80 to re-capture, re-evaluate or refine the processthe eye 80. Thus, the relative positions of the iris 84 and theprocedure equipment can be kept correct at all times.

[0070] Referring now to FIG. 7, there is shown the illuminationfrequency optimization system 130. The illumination frequencyoptimization system 130 is an alternate embodiment of the aberrationcorrecting system 10. Within the frequency optimization system 130 avariable frequency light source 132 rather than a single frequency lightsource applies a light beam to the eye 80. The variable frequency lightsource 132 can be a tunable laser, a diode, filters in front of a lightsource, a diffraction grating or any other source of a plurality offrequencies of light. An image quality metric can be obtained andoptimized in the manner previously described with respect to system 10.

[0071] Using the variable frequency light source 132, it is possible toconveniently adjust the frequency of the light beam used to illuminatethe eye 80 or object 80 at a plurality of differing frequencies and toobtain a plurality of corresponding image quality metrics. In order todo this, the frequency of the light applied to the eye 80 by thevariable frequency light source 132 can be repeatedly adjusted and a newimage quality metric can be obtained at each frequency. Each imagequality metric obtained in this manner can be optimized to apredetermined level. The levels of optimization can be equal or they candiffer. While the optimizations should be done using the frequencydistribution, it is possible to return to images optimized using thefrequency distribution and sharpen using the sharpness function.

[0072] It is well understood that differing types of tissue can bevisualized best with differing frequencies of light. For example,tumors, lesions, blood and various tissues as well as tissues of varyingpathologies can be optimally visualized at different frequencies sincetheir absorption and reflection properties vary. Thus, by adjusting thefrequency applied to the eye 80 by the variable frequency light source132 and viewing the results, the best light for visualizing selectedfeatures can be determined. Furthermore, using this method there can beseveral optimized images for one eye. For example, there can bedifferent optimized images, for a tumor, for a lesion and for blood. Thedetermination of the best frequency for each image can be a subjectivejudgment made by a skilled practitioner.

[0073] A skilled practitioner can use the illumination frequencyoptimization system 130 to emphasize and de-emphasize selected featureswithin images of the eye 80. For example, when obtaining an irisbiometric image 95, the iris 84 may be clouded due to inflamation of theeye 80 or the presence of blood in the eye 80. It is possible toeffectively remove the effects of the inflamation blood with theassistance of the frequency optimization system 130 by varying thefrequency of the light provided by the light source 132 until theoptimum frequency is found for de-emphasizing the inflammation or bloodand permitting the obscured features to be seen. In general, it is oftenpossible to visualize features when another feature is superimposed onthem by removing the superimposed feature using system 130.

[0074] In order to remove the effects of the inflamation or blood, aplurality of images of the eye 80 can be provided and the frequency atwhich the blood or inflamation is least apparent can be determined.Removing these features from the iris biometric image 95 can facilitateits comparison with the iris biometric image 90. Furthermore, when thebiometric image 95 is obtained from the iris 110 of a person wearingsunglasses, it is possible to remove the effects of the sunglasses inthe same manner and identify an eye 80 behind the sunglasses. Thisfeature is useful when identifying people outside of laboratoryconditions.

[0075] Referring now to FIG. 8, there is shown the image superpositionsystem 150. In many cases it is desirable to perform a procedure on aneye 80 when selected features of the eye 80 are obscured by otherfeatures, where different features are visualized best at differentfrequencies, or where the criteria for emphasizing and de-emphasizingfeatures can change during a procedure. Image superposition 100 can beused to obtain improved feature visualization under these and othercircumstances.

[0076] For example, white light is often preferred for illuminating aniris 84 because in many cases white light shows the most features.However, if white light is used to illuminate an iris 84 when the iris84 is clouded with blood, the blood can block the white light. This canmake it difficult, or even impossible, to visualize the features thatare obscured by the blood. One solution to this problem is to use redlight to illuminate the iris 84 and visualizes the features obscured bythe blood.

[0077] However, the red light could fail to optimally visualize thefeatures which are normally visualized best using, for example, whitelight. The image superposition system 150 can solve this problem bysuperimposing two images such as the direct image 166 and the projectedimage 170, where the images 166, 170 are obtained using light sources ofdiffering frequencies. The optimum frequencies for obtaining each of theimages 166, 170 can be determined using the illumination frequencyoptimization system 130.

[0078] For example, an object 168 to be visualized can be illuminatedwith incoherent white light to provide the direct image 166.Illumination of the object 168 by white light to produce the directimage 166 can be provided using any of the known methods for providingsuch illumination of objects to provide digital images. The direct image166 can be sensed and digitized using an image sensor 152 which senseslight traveling from the object 168 in the direction indicated by thearrows 156, 164.

[0079] The image sensor 152 senses the direct image 166 of the object168 by way of a superposition screen 160. The superposition screen 160can be formed of any material capable of transmitting a portion to thelight applied to it from the object 168 to the image sensor 152, andreflecting a portion of the same light. For example, the superpositionscreen 168 can be formed of glass or plastic. A viewer, a TV screen or agradient filter can also serve as the superposition screen 160. Thescreen 160 can also be a gradient filter. In a preferred embodiment ofthe invention, the angle 172 of the superposition screen 160 can beadjusted to control the amount of light it transmits and the amount itreflects.

[0080] The projected image 170 of the object 168 can be obtained using,for example, the aberration correcting system 10 as previouslydescribed. Illumination with red light or any other frequency of lightcan be used within the aberration correcting system 10 to obtain thesuperposition image 178. The superposition image 178 is applied to animage projector 176 by the aberration correcting system 10. The imageprojector 176 transmits the projected image 170 in accordance with thesuperposition image 178 in the direction indicated by the arrow 174 andapplies it to the superposition screen 160.

[0081] A portion of the projected image 170 applied to the superpositionscreen 160 by the projector 176 is reflected off of the superpositionscreen 160 and applied to the image sensor 152 in the directionindicated by the arrow 156. The amount of the projected image 170reflected to the image sensor 152 can be adjusted by adjusting the angle172 of the superposition screen 160. The image projector 176 is disposedin a location adapted to apply the projected image 170 to thesuperposition screen 160 in the same region of the superposition screen160 where the direct image 166 is applied. When the images 166, 170 areapplied to the superposition screen 160 in this manner, they aresuperimposed and the image sensed by the image sensor 152 is thus thesuperposition or composite of the images 166, 170.

[0082] Adjustment of the angle 172 results in emphasizing andde-emphasizing the images 166, 170 relative to each other. This isuseful, for example, where different features visualized selectively atdiffering frequencies must be brought in and out of visualization in thecomposite image for different purposes. Another time where this isuseful is when the intensity of one of the images 166, 170 is too highrelative to the other and must be adjusted down or too low and must beadjusted up.

[0083] In various alternate embodiments of the image superpositionsystem 150, either or both of the images 166,170 can be optimized usingthe PSPGD algorithm 20 within the aberration correction system 10.Furthermore, the images 166, 170 can be optimized to differing degreesby the PSPGD algorithm 20 and with differing optimization criteria inorder to emphasis one over the other or to selectively visualizeselected features within the images 166,170 and thus, within thecomposite image sensed by image sensor 152. This permits selectedfeatures of the eye 80 to be brought into view and brought out of viewas convenient at different times during a diagnosis or a procedure.

[0084] Thus, the illumination used to obtain the images 166, 170superimposed by the image superposition system 150 does not need to bered and white light. The illumination used can be light of any differingfrequencies. The frequencies selected for obtaining the images 166, 170can be selected in accordance with the sharpness function on thefrequency distribution as previously described.

[0085] The images superimposed by the image superposition system 150 donot need to be obtained by way of a camera, such as the camera 6 of theaberration correction system 10. A microscope, an endoscope, or anyother type of device having an image sensor capable of capturingtransmission, absorption or reflection properties of an object or tissuein a normal state or enhancement by such materials as markers andchromophores and thereby providing an optical/digital signal that can beapplied to the computer 7 for optimization using the PSPGD algorithm 20can be used. Thus, for example, an image obtained from an endoscope or amicroscope can be superimposed upon an image obtained from an camerausing the method of the present invention. Images from endoscopes,microscopes and other devices can be digitized, and superimposed andsynthesized with each other. It will be understood that images obtainedfrom such devices and optimized using the PSPGD algorithm 20 can be usedin any other way that images obtained from the PSPGD algorithm 20 usingcamera 6 are used.

[0086] The description herein will so fully illustrate my invention thatothers may, by applying current or future knowledge, adopt the same foruse under various conditions of service. For example, the invention maybe used for ophthalmological procedures such as photocoagulation,optical biopsies such as measuring tumors anywhere in the eye, providingtherapy, performing surgery, diagnosis or measurements. Additionally, itcan be used for performing procedures on eyes outside of laboratory ormedical environments. Furthermore, the method of the present inventioncan be applied to any other objects capable of being imaged in additionto eyes and images of an object provided. In accordance with the methodof the invention can be used when performing such procedures on otherobjects.

[0087] While the invention has been described in detail and withreference to specific examples thereof, it will be apparent to oneskilled in the art that various changes and modifications can be madetherein without departing from the spirit and scope thereof.

What is claimed is:
 1. A method for optimizing electromagnetic energy ina system for processing an image of an object in order to perform aprocedure on an object, comprising the steps of: (a) applying to anobject a plurality of light beams formed of incoherent light at aplurality of differing frequencies and reflecting said plurality ofapplied incoherent light beams from said object to provide a pluralityof reflected light beams; (b) providing a corresponding plurality ofelectrical signals representative of the reflected light beams of saidplurality of reflected light beams; (c) determining a correspondingplurality of image quality metrics in accordance with said plurality ofelectrical signals; (d) determining a corresponding plurality of imagesin accordance with said plurality of image quality metrics; (e)selecting an image of said plurality of images in accordance with apredetermined image criterion to provide a selected image; (f)determining a frequency of said plurality of differing frequencies inaccordance with said selected image to provide a determined frequency;and (g) performing said procedure on an object in accordance with saiddetermined frequency.
 2. The method for optimizing electromagneticenergy of claim 1, comprising the further step of determining aplurality of frequency distributions in accordance with said pluralityof differing frequencies.
 3. The method for optimizing electromagneticenergy of claim 2, comprising the further step of determining aplurality of image quality metrics in accordance with said plurality offrequency distributions.
 4. The method for optimizing electromagneticenergy of claim 3, comprising the further step of optimizing an image ofsaid plurality of images.
 5. The method for optimizing electromagneticenergy of claim 1, wherein said predetermined image criterion isselected in accordance with the light absorption properties of aselected tissue.
 6. The method for optimizing electromagnetic energy ofclaim 5, wherein said selected tissue comprises tumor tissue.
 7. Themethod for optimizing electromagnetic energy of claim 5, wherein saidselected tissue comprises lesion tissue.
 8. The method for optimizingelectromagnetic energy of claim 5, wherein said selected tissuecomprises blood tissue.
 9. The method for optimizing electromagneticenergy of claim 5, wherein said predetermined image criterion isselected in accordance with the light absorption properties of a tissuepathology.
 10. The method for optimizing electromagnetic energy of claim5, comprising the further step of locating said selected tissue in aneye of a patient in accordance with determined frequency.
 11. The methodfor optimizing electromagnetic energy of claim 5 comprising the furthersteps of: (a) applying a further light beam of said determined frequencyto a selected tissue; and (b) performing surgery upon said selectedtissue in accordance with said further light beam.
 12. The method foroptimizing electromagnetic energy of claim 5, wherein said eye has aselected tissue feature comprising the further step of determiningchanges in said selected tissue feature in accordance with saiddetermined selected light frequency.
 13. The method for optimizingelectromagnetic energy of claim 4, comprising the further step ofapplying said plurality of reflected light beams to a spatial lightmodulator and an image sensor to provide said plurality of signalsrepresentative of said reflected light beams.
 14. The method foroptimizing electromagnetic energy of claim 13, further comprising thestep of determining said plurality of image quality metric in accordancewith said signals representative of said reflected light as:J=∫|F{exp[iγI(x,y)]}|⁴ dxdy where F is a Fourier transform and ã is aparameter dependent upon a dynamic range of said reflected light beam.15. The method for clarifying an optical/digital image of an objectclaim 1, comprising the further steps of: (a) applying to said object asuperposition light beam and reflecting said superposition light beamfrom said object to provide a reflected superposition light beam; (b)providing a superposition image in accordance with said reflectedsuperposition light beam; and (c) superimposing said selected image andsaid superposition image to provide a composite image
 16. The method forclarifying an optical/digital image of an object of claim 15, comprisingthe further step of performing said procedure in accordance with saidcomposite image.
 17. The method for clarifying an optical/digital imageof an object of claim 16, comprising the further step of applying saidselected image and said superposition image to a superposition screen inorder to provide said composite image.
 18. The method for clarifying anoptical/digital image of an object of claim 17, wherein said object hasa selected feature comprising the further step of optimizing at leastone of said selected image and said superposition image to emphasize avisualization of said selected feature.
 19. The method for clarifying anoptical/digital image of an object of claim 18, wherein said object isan eye comprising the further step of de-emphasizing a visualization ofblood.
 20. The method for clarifying an optical/digital image of anobject of claim 18, comprising the further step of adjusting an amountof emphasizing of said visualization during a performance of saidprocedure.
 21. The method for clarifying an optical/digital image of anobject of claim 20, comprising the further step of adjusting an amountof emphasizing of said selected feature by adjusting the relativecontributions of said selected image and said superposition image tosaid composite image.